The top seven vertebrae in the spine, vertebrae C1 through C7, form the cervical spine. Adjacent vertebrae in the cervical spine interface at two sets of opposing articulated surfaces each with an intervertebral disc. Trauma to the cervical spine, degenerative conditions such as arthritis and genetic disorders can cause fractures in the vertebrae, damage to intervertebral discs, pressure on the spinal cord or other nerves and misalignment or improper spacing between adjacent vertebrae. The result is pain, discomfort and other symptoms including periods of confusion or conscious awareness that does not seem normal, difficulty swallowing or saying words due to loss of muscle control after damage to the nervous system (dysarthria), dizziness, loss of sensation, pain in the back of the head, loss of the ability to know how joints are positioned, tingling or numbness in the hands or fingers, tingling or numbness in the arms, tingling when the neck bends forward or backward and weakness or stiff and awkward movements of the of the arms and legs.
One such condition is basilar invagination, which occurs when the top of the C2 vertebra, e.g., the axis, migrates upward toward the C1 vertebra, e.g., the atlas. As the base of the skull rests on the C1 vertebra and the odontoid process extends from the axis up though the atlas, this upwards migration can cause the opening in the skull where the spinal cord passes through to the brain to narrow and may also press on the lower brainstem. Treatment for basilar invagination and other symptoms associated with other conditions in the cervical spine includes both surgical and non-surgical techniques.
While some patients respond well to non-surgical treatments, others require surgery. These surgical techniques include replacing discs and repairing vertebrae using bone grafts. A cervical plate is screwed into the superior and inferior vertebral bones, which stabilizes the cervical spine facilitating fusion and healing. In addition, screws are used to mend fractured vertebrae including a fractured odontoid process. Maintaining proper alignment and spacing between adjacent vertebral bones is important. The use of a screw passing between the adjacent articular facets does not guarantee that the proper spacing is maintained. In addition, re-establishing and maintaining proper spacing between the axis and the atlas can prevent or alleviate basilar invagination.